Heating, Air Conditioning, Fridge, HVAC/drain pan


QUESTION: Recently i  noticed the overflow was leaking outside my house. I assumed that the primary drain was clogged.  I vacuumed the line from the vent after the p-trap then I also vacuumed from the end of the line where it connects to the bathroom sink.  Would work for awhile then i Would notice the overflow drain draining again.  I then took off the cover and exposed the coils.  What I found here was the pan would fill with water and would not drain from either drain until the unit shut down.  Once unit shut down then the water would drain from both drain holes. How do I correct this


New unit? old unit? did it work OK last year. Try trapping the secondary drain .Both drains should be 3/4" ID and pitched significantly for proper drainage. If this is an old system try using your wet dry vac and clean the evaporator pan itself. new unit? if so possible your trap outlet is not low enough compared to the inlet side of the trap. Also I seen a vent on the primary drain line downstream of the air handler, a few feet past the Air Handler. Install a Tee in the drain line near the AH and add a short vertical piece of drain line approx. 6 " to 8" open to the atmosphere. That should release any negative pressure that you may have and your condensate should drain while running.

In closing 3/4" ID drain line for residential unit , make sure Air Handler is level both ways . Consider installing a trap on the secondary drain, verify you have the correct pitch for proper drainage. verify the trap outlet side is at least one inch lower than the inlet side. Clean the Evaporator drain pan of any sediments. Install the vent in the drain line ( a tee and a small vertical piece aprox. 6" to 8" to release the negative pressure for free drainage )

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QUESTION: This is an older unit(ten years old), and have not had any problems with it in the past. I have used wet/dry vac and cleaned the pan the best I could. I have enclosed a pic for your viewing. Also this is not the only unit I have. There is a second unit just like this one and it is plumbed the exact same way.  That one is not having any problems draining. I could put a trap on the secondary drain pipe, but there has not been one there for the past ten years. Again it drains properly when the fan shuts down.


Your suppose to flush or blow out drain lines occasionally, not when they don't work. There is a reason they come with aux. drains, I would hook up both lines with traps. or tie in the aux. drain downstream of the primary trap into the primary drain line. I make my own traps with a clean out drain at the trap. All you need is street elbows, regular elbows and one tee with a screw in cap. You state " I vacuumed the line from the vent after the p-trap then I also vacuumed from the end of the line where it connects to the bathroom sink."  If the line that goes to the bathroom sink is open and you hooked to this end, air is going to take the path of least resistance, it's NOT going to pull sediment from the trap the air will enter from your vertical vent bypassing the trap. You state you suck from the vertical vent also ,again if the trap is partially blocked air takes the path of least resistance and will pull air from the sink end outlet. Also your aux. drain line should be plugged or hooked up,yours looks to open to the atmosphere. You did not state you plugged the vertical line while you used the wet/dry vac at the sink drain to clean the trap or vise versa.

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40+ years diversified experience.An HVAC/Refrigeration Self Employed Contractor since 1986. NATE Certifield. Answer questions pertaining to Residential and Commercial Air Conditioning , Warm Air Heating, Heat Pump systems.Mechanical and Electrical troubleshooting of these systems.Be as detailed as possible when describing problem.Packaged unit or split systems.No appliance questions.


Installation and Troubleshooting, Mechanical and Electrical, in following areas, Refrigeration ( Walk In and Reach In Coolers and Freezers ) Commercial Roof Top and Packaged Heating/Cooling ( Natural Gas,Propane, Electric, and Heat Pumps ) Computer Room Air Conditoning Systems,Commercial Residential Packaged and Split Systems Air Conditoning and Heat Pumps.Warm Air Oil , Natural and Propane Gas Heating systems.

Graduated from Private Technical School in 1975. An HVAC/Refrigeration Contractor . Have Unlimited Heating/Piping and Cooling Contractor License.Limited Sheetmetal Contractors License.NATE Certifield. York Certifield Master Heat Pump Technician 1986. Served 33 years combination Active Duty Air Force , Air Force Reserves and Air National Guard in the HVAC/Refrigeration Shop/Mechanical Shop. Troubleshooting/Installing HVAC/Refrigeration Equiptment Worldwide. Retiring in 2003 as a Senior NCO ,and a Mechanical Superintendent.

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